Use of lipophilic additives for the improvement of the characteristics of PVC membrane lithium-selective electrodes based on non-cyclic neutral carriers

Abstract

Favourable effects were found for poly(vinyl chloride)(PVC) membrane lithium-selective electrodes based on synthesised non-cyclic neutral carriers to which a lipophilic salt in combination with organophosphorus compounds had been added. Tetrabutylammonium tetraphenylborate as a lipophilic salt appreciably increased the selectivity for lithium over alkali metal ions when used in combination with trioctylphosphine oxide in the ion-sensitive membrane. The selectivity coefficient –log k^pot_Li,M increased from 1.5 to 2.2 for Li⁺ over Na⁺ and from 2.0 to 3.0 for Li⁺ over K⁺ by the addition of these compounds. The results obtained here are of practical use in developing lithium-selective electrodes, as the proposed additives have been shown to exert positive effects on several kinds of non-cyclic lithium-selective carriers in PVC matrix ion-selective electrodes.